In a power window device of a vehicle, which has a foreign object pinching restricting function, it is proposed to differentiate reversing timing of window glass according to hardness of a foreign object that is pinched between a vehicle chassis and the window glass (for example, JP 2001-248358A). In this manner, by differentiating the reversing timing according to the hardness of the foreign object pinched, an excessive pinch load can be reduced from being applied to the foreign object pinched.
Generally, in the power window device like this, a rotation speed and a rotation speed difference of an electric motor, which are used for calculating a pinch load, are calculated based on a speed signal (for example, a pulse signal) from a rotation speed sensor arranged in the electric motor. In such calculation processing, in order to cancel error variation amounts of the rotation speed and the rotation speed difference, a moving average of a plurality of temporally sequential calculated values is calculated. Therefore, the pinch load that is calculated includes a delay as compared to an actual pinch load.
Thus, due to this delay in detection timing, by the time the pinch load is calculated by a pinching detecting part, a load will have already been applied to the foreign object according to its properties such as the hardness or deformability. For this reason, when a detected load reaches a predetermined value, the pinch load in accordance with its properties is practically applied to the foreign object, that is, the excessive pinch load is applied.
As well, in a case where a soft object is pinched, because the foreign object is deformed while initially pinched by the window glass, the pinch load hardly increases. Thus, after the foreign object is deformed to some extent, the pinch load starts to increase. The pinching detecting part can detect pinching when the pinch load increases and the detected load reaches the predetermined value.
Hence, even if a soft foreign object is pinched by the window glass, the detected load does not reach the predetermined value unless a certain amount of time elapses including a period during which the foreign object is deformed. Consequently, the foreign object remains constrained to the window glass for a relatively long time with a reversing operation of the window glass unperformed.
Moreover, since the electric motor and a drive mechanism, which are included in a drive part that moves up and down the window glass, have play and a backlash, a decrease in the rotation speed of the electric motor is absorbed by the play and the backlash during an initial phase of the pinching by the window glass.
The pinching detecting part calculates the pinch load (a pinched amount) from a variation (the decrease) and the like in the rotation speed (the number of rotations) of the electric motor, but timing is delayed with which the rotation speed of the electric motor starts to decrease due to the play and the backlash during the initial phase of the pinching. As a result, the timing is delayed with which the detected load starts to increase, thereby delaying the timing with which the detected load reaches the predetermined value. Accordingly, the foreign object remains constrained to the window glass for the relatively long time with the reversing operation of the window glass unperformed.